1. Field of the Invention
This invention relates to a camera having motorized film winding and rewinding capabilities.
2. Description of the Related Art
To motorize the transporting of film in making an automatic camera, there are the following two transportation methods:
(1) Setting a film cartridge.fwdarw.automatic loading with blank advance (equivalent usually to three frames) to the first frame usable for shooting.fwdarw.winding the film by one frame for every shot.fwdarw.detecting the film end.fwdarw.transporting all the exposed frames backward thus rewinding the entire length of the pulled-out film into the cartridge.
(2) Setting a film cartridge.fwdarw.pre-winding the film so that all usable frames are previously wound onto the takeup spool.fwdarw.transporting the film backward by one frame for every shot.fwdarw.after the last usable frame has been exposed, rewinding the remaining area of the film continuously into the cartridge.
With the camera employing the above-described method (1), however, the time lag from the termination of the exposure of the last frame in the preceding film cartridge to the initiation of an exposure of the first frame in the current film cartridge is very long, because the completion of exposing all film has to be followed by the rewinding of the film through the entire length.
In the camera of the above-described method (2), the first shot cannot be taken until the film is all of the frames of film are unwound from the film cartridge upon its being loaded into the camera. Hence, the film exchange also results in a long time lag to the start of shooting.
The minimization of a time it takes to continuously wind or rewind the film through the length of all frames is restricted by the electrical power source, the motors, etc. the camera is able to accommodate. Taking an example of 36-exposure film, even the fast camera takes some 10 seconds, while the slow camera consumes a longer time than 20 seconds. This means that, for the professional cameraman or the equivalent, it will happen in some cases that good shutter chances are missed by the time lag of 10 to 20 seconds as the film is exchanged. An improvement is desired.
So, a previous proposal for the improvement has been made in which once the winding lever is cocked, the film is advanced through the length of two frames so that every other frame is exposed in sequence as the film is wound, and, after the film has been wound up to all the frames, the remaining every other frame starts to be exposed in sequence as the film is rewound by the same winding lever. Cameras of such a two-way exposure type are known in Japanese Patent Publications. Nos. Sho 42-7827 and Sho 48-43810 and others.
In addition, Japanese Laid-open Patent Application No. Hei 1-202723 discloses that the above-described advancing of film is performed by motor drive.